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Introduction: Early detection of bladder cancer increases the chances of successful treatment. pHLIP is a peptide that specifically targets acidic tissue. Conjugated with near infrared ICG dye, a ICG-pHLIP construct successfully differentiates normal from cancerous tissue. We performed ex vivo imaging of human bladder cancer on cystectomy specimens after intravesical instillation of ICG-pHLIP.
Materials & Methods:Fourteen patients undergoing radical cystectomy over a five month period were included. The da Vinci Si NIRF imaging system (FireflyR) was used to capture ICG-pHLIP NIRF signal. After removal, bladders were instilled with ICG-pHLIP construct for 1 hour. The bladder was then washed, opened and imaged. ICG-pHLIP fluorescent signal was recorded, tissue was marked for NIRF signal presence and pathologic analysis was performed to correlate with NIRF signals.
Results: Thirteen cancerous bladders were targeted by ICG-pHLIP with accurate correlation on final pathology. Six patients had CIS and 2 patients showed high grade dysplasia which likewise was targeted by ICG-pHLIP. In only one case high grade NMIBC and CIS showed no uptake of ICG-pHLIP. NIRF imaging sensitivity and specificity were 92.86% (95%CI 66.06-98.81) and 93.33% (95% CI 67.98-98.89%) respectively.
Conclusions: NIRF imaging using ICG-pHLIP successfully targets cancerous acidic tissue in ex vivo bladder specimens. NIRF signal was absent in normal bladder mucosa. This is the first study to show efficient pH dependent NIRF imaging of bladder tumors. The ICG-pHLIP construct could be developed into a novel predictive clinical marker, targeting the acidic environment of bladder tumors after intravesical administration.